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Test ID DHRF Dihydrorhodamine Flow Cytometric N-Formyl-Methionyl-Leucyl-Phenylalanine Test, Blood

Useful For

Diagnosis of Rac2 deficiency

Reporting Name

DHR Flow fMLP, B

Specimen Type

WB Sodium Heparin

Shipping Instructions

Specimens are required to be received in the laboratory weekdays and by 4 p.m. on Friday. Draw and package specimen as close to shipping time as possible. Ship specimen overnight in an Ambient Shipping Box-Critical Specimens Only (T668) following the instructions in the mailer.


It is recommended that specimens arrive within 24 hours of draw.


Samples arriving on the weekend and observed holidays may be canceled.

Necessary Information

Ordering physician name and phone number are required.

Specimen Required

Both a whole blood sodium heparin specimen and a whole blood sodium heparin control specimen from an unrelated, healthy donor are required.


Supplies: Ambient Shipping Box-Critical Specimens Only (T668)



Container/Tube: Green top (sodium heparin)

Specimen Volume: 5 mL

Collection Instructions: Send specimen in original tube. Do not aliquot.


Normal Control:

Container/Tube: Green top (sodium heparin)

Specimen Volume: 5 mL

Collection Instructions:

1. Draw a control specimen from a normal (healthy), unrelated person within an hour of the patient.

2. Label clearly on outermost label normal control.

3. Send specimen in original tube. Do not aliquot.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
WB Sodium Heparin Ambient 48 hours GREEN TOP/HEP

Clinical Information

This assay can be used for the diagnostic evaluation of Rac2 deficiency, which is a neutrophil defect that causes profound neutrophil dysfunction with decreased chemotaxis, polarization, superoxide anion production, azurophilic granule secretion. This disease is caused by inhibitory mutations in the RAC2 gene, which encodes a Rho family GTPase essential to neutrophil activation and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase function.(1) Patients with Rac2 deficiency have been shown to have normal neutrophil oxidative burst when stimulated with phorbol myristate acetate (PMA), indicating normal NADPH oxidase activity, but abnormal neutrophil responses to N-formyl-methionyl-leucyl-phenylalanine (fMLP), which is a physiological activator of neutrophils. The defective oxidative burst to fMLP, but not to PMA, indicates a signaling defect in Rac2 deficiency.(2)

Reference Values

Result Name


Cutoff for defining normal

% fMLP ox-DHR+






Control % fMLP ox-DHR+



Control MFI fMLP ox-DHR+




The appropriate age-related reference values for Absolute Neutrophil Count will be provided on the report.


An interpretive report will be provided, in addition to the quantitative values described in Clinical Information.


Interpretation of the results of the quantitative dihydrorhodamine (DHR) flow cytometric assay has to include both the proportion of positive neutrophils for DHR after N-formyl-methionyl-leucyl-phenylalanine stimulation, and the mean fluorescence intensity.

Clinical Reference

1. Ambruso DR, Knall C, Abell AN, et al: Human neutrophil immunodeficiency syndrome is associated with an inhibitory Rac2 mutation. Proc Natl Acad Sci U S A 2000;97:4654-4659

2. Accetta D, Syverson G, Bonacci B, et al: Human phagocyte defect caused by a RAC2 mutation detected by means of neonatal screening for T cell lymphopenia. J Allergy Clin Immunol 2011;127:535-538

Day(s) Performed

Monday through Friday

Report Available

3 to 4 days

Test Classification

This test was developed using an analyte specific reagent. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
DHRF DHR Flow fMLP, B 98123-3


Result ID Test Result Name Result LOINC Value
ANC Absolute Neutrophil Count 751-8
FMPPP % FMLP ox-DHR+ 85373-9
FMPM MFI fMLP ox-DHR+ 85370-5
ANCC Control Absolute Neutrophil Count 85369-7
FMPPC Control % fMLP ox-DHR+ 85372-1
FMPMC Control MFI fMLP ox-DHR+ 85371-3
DHRFI Interpretation 69052-9

Method Name

Flow Cytometry